import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';

const MIN_LOADING_TIME = 300;

export interface ILoadingConfig {
    readonly type: 'spinner' | 'progress-bar';
    readonly title?: string;
    readonly value?: number;
    readonly remainingTime?: string;
}

@Injectable({ providedIn: 'root' })
export class LoadingService {
    readonly #loadingEvent$ = new BehaviorSubject<ILoadingConfig | undefined>(undefined);
    readonly isLoading$ = this.#loadingEvent$.asObservable();
    #loadingStarted = 0;
    #timeout?: number;

    start(config: ILoadingConfig = { type: 'spinner' }): void {
        if (this.#timeout) {
            clearTimeout(this.#timeout);
            this.#timeout = undefined;
        }
        setTimeout(() => {
            this.#loadingEvent$.next(config);
            this.#loadingStarted = new Date().getTime();
        });
    }

    update(config: ILoadingConfig): void {
        if (!this.#loadingEvent$.value) {
            return this.start(config);
        }
        this.#loadingEvent$.next(config);
    }

    stop(): void {
        const timeSinceStarted = new Date().getTime() - this.#loadingStarted;
        const remainingLoadingTime = MIN_LOADING_TIME - timeSinceStarted;

        return remainingLoadingTime > 0 ? this._stopAfter(remainingLoadingTime) : this._stop();
    }

    loadWhile(func: Promise<unknown>): void {
        this.start();

        func.then(
            () => this.stop(),
            () => this.stop(),
        );
    }

    private _stop(): void {
        setTimeout(() => this.#loadingEvent$.next(undefined));
    }

    private _stopAfter(timeout: number): void {
        this.#timeout = window.setTimeout(() => this._stop(), timeout);
    }
}